The purpose of this project is to conduct a clinical evaluation of the safety, immunogenicity and efficacy in children in an endemic area of investigational vaccines designed to prevent shigellosis. The contractor is to perform Phase 2 study (safety and immunogenicity) of Shigella flexneri type 2a EPA and S. sonnei EPA conjugate vaccines in children aged 4 to 6 years old. Each vaccine shall be injected into 50 children, ages 4 to 6 years old. A total of 100 children shall be vaccinated. One hundred children, who have received the Hepatitis B vaccine shall serve as controls for this study. This project has been approved by the NIH (Protocol Number OH94-CH-NO94) and FDA (BB-IND-4331-S. Sonnei and BB-IND- 3866-S. flexneri).